Messaging Hygiene at Microsoft
Detailed discussion on how Microsoft IT manages the large quantities of unwanted e-mail (a.k.a. spam) and malware-infected messages in its inbound Internet e-mail traffic.
You can download it at http://www.microsoft.com/downloads/details.aspx?familyid=17dc35ad-8ba1-48b1-91f3-563313ee878a&displaylang=en